1. Field of the Invention
This invention relates to an outboard engine assembly wherein an engine room concealed by an engine cover is divided into a heat-side room section and an air-intake-side room section.
2. Description of the Related Art
Various outboard engine assemblies employing a V-type engine which meets a demand for discharging exhaust emissions at a large flow rate to provide an increased engine power output while attaining miniaturization of an external size of the engine are known. A typical example of such engine assemblies is disclosed in Japanese Patent Laid-Open Publication No. HEI-5-30663.
Generally, the outboard engine assembly equipped with an engine functions to intake air in an engine room which is defined with an engine cover. Accordingly, the surrounding temperature in the engine room is adversely affected with the temperature of intake air, resulting in a decrease in engine power output or causing a difficulty in startup of the engine.
To address this issue, it has been proposed to employ a partition plate in the outboard engine assembly for separating intake air from a heat source, as disclosed in Japanese Patent Laid-Open Publication No. HEI-6-016187.
The outboard engine assembly, disclosed in Japanese Patent Laid-Open Publication No. HEI-6-016187, has the partition plate which defines an internal space in an engine cover receiving the engine into a main space and a sub space which are aligned in fore and aft direction in the outboard engine assembly. The sub space receives a throttle body, and the main space receives major part of the engine. The sub space communicates with an air intake port formed at a front portion of the engine cover for combustion. Consequently, the outboard engine assembly is designed on the assumption that an air intake system is located in front of a crankcase, with a resultant difficulty caused in applying such a concept in the aforementioned V-type engine.
In recent years, outboard engine assemblies having an alternating-current generator (alternator) driven by a crankshaft through a belt are now widely used on boats. It has been proposed to provide an outboard engine assembly with a watertight cover which conceals the generator to prevent entry of water from the outside air introducing port formed in the engine cover for combustion, as known for example from Japanese Patent Laid-Open Publication No. HEI-6-33790. The generator is located at an area remotest from the air intake system.
In the aforementioned outboard engine, however, the absence of consideration of hot air produced by the generator leads to a difficulty in effectively cooling the alternating-current generator. In the halt state of the engine, further, hot air is filled in the watertight cover and the engine room, causing hot air to be undesirably sucked into the engine due to intake vacuum produced during re-startup of the engine.
With such an engine room having a narrow space, mounting the alternating-current generator in a position separated from air flow directed to the intake air introducing port of the engine undergoes an issue to restrict the freedom in designing the outboard engine assembly. In contrast, simply increasing the engine room with a view to separating the generator from the aforementioned air flow encounters another problem caused in a large size of the outboard engine assembly.
To address these issues, it has been proposed to provide an outboard engine assembly wherein the alternating-current generator is located in a midway of an air flow passage leading from the intake air introducing port formed in the engine cover and the air intake system in order to effectively cool the generator, as suggested by Japanese Patent Laid-Open Publication Nos. HEI-10-184377 and HEI-11-198893 filed by the applicant of this application.
It is therefore an object of the present invention to provide an outboard engine assembly having an effective engine room structure, suited for use in an engine wherein a crankcase and an intake air introducing port are separated from one another, and an outboard engine structure of the V-type engine.
According to a first aspect of the present invention, there is provided an outboard engine assembly which comprises an engine having a cylinder block with at least one cylinder forming part of a combustion chamber, a cylinder head, a cylinder head cover and a crankcase accommodating a crankshaft in vertical orientation, an engine cover located so as to cover a periphery of the engine and forming an engine room or engine compartment which receives the engine, an air intake passage communicating the engine room with the combustion chamber, wall means located at an outer side area of the cylinder head cover and dividing the engine room into a least two room sections, an engine-room-side communicating section connected to the air intake passage located in one of the room sections divided by the wall means, and exhaust means located in another one of the room sections divided by the wall means and communicating with the combustion chamber.
With such a feature of the present invention, the wall means, which constitutes a partition wall to divide the engine room, utilizes a flat portion of an outer wall surface of the cylinder head cover, with a resultant ease of installation of the wall means (wall partition). The presence of the wall means makes it possible to reliably divide the engine room for thereby effectively lowering the temperature of intake air. Since the wall means is simply placed between an outer wall surface of the cylinder head cover and an inner wall surface of the cylinder cover, the wall means has a reduced number of component parts and makes it possible to adopt a thick string made of urethane rubber or sponge with a circular cross section. Thus, the wall means per se has a sealing property, making it unnecessary to use an extra sealing member such as a partition plate.
In particular, even in the engine wherein the crankcase and the intake air introducing port are separated from one another, the division of the engine room is reliably ensured with the wall means such that, especially in the V-type engine, the air intake unit is located in the V-bank to reliably ensure the engine room to be divided into fore and aft room sections.
In a preferred form, the engine assembly employs the V-type engine wherein the aforementioned cylinder blocks are configured in the V-shape. Locating the wall means, which constitutes the partition wall, by utilizing the outer sides expanded in the V-shape of the V-type engine requires a decreased amount of extension (which is not a vertical length but is the amount of protrusion in the engine room). Specifically, in a case of the engine cover which is configured in a deeply shaped bowl profile facing downward, the presence of the wall means having the reduced extension enables the production in an easy manner. In the outboard engine assembly mounted with the V-type engine, further, the location of the air intake unit in the V-bank ensures the division of the engine room in the fore and aft room sections. Consequently, in the outboard engine assembly mounted with the V-type engine, it is possible to effectively lower the temperature of intake air.
Preferably, the cylinder head cover is composed of a material such as, for example, a plastic resin. With the cylinder head cover made of plastic material, it is possible to minimize the wear of the engaging portions (abutting engagement portions) of the cylinder head cover relative to the wall means owing to the vibrations of the engine. Also, while a cam chamber is defined by the cylinder head having a heat and the cylinder head cover, the presence of the cylinder head cover made of plastic material eliminates the amount of heat transfer from the cylinder head side, with a resultant increase in the performance of lowering the temperature of intake air.
It is desirable that the intake air silencer is located in the intake air passage above the cylinder block. Location of the intake silencer at an area above the engine enables the wall means to provide an efficient sealing effect with the use of a relatively flat surface of the intake silencer. Also, the presence of the intake silencer located above the engine enables the wall means to be readily extended over an area starting from the starboard side to the port side, providing an ease of locating the wall means as well as ensuring the sealing property.
According to a second aspect of the present invention, there is provided an outboard engine assembly which comprises an engine having a cylinder block with at least one cylinder forming part of a combustion chamber, a cylinder head, a cylinder head cover and a crankcase accommodating a crankshaft in vertical orientation, an engine cover located so as to cover a periphery of the engine and forming an engine room which receives the engine, and wall means located between an engine-room-side communicating section of the intake air passage of the engine, and an alternating-current generator mounted to the engine.
The presence of the wall means, which serves as the partition wall, located between the room section for the alternating-current generator and the room section for the intake air side in the engine room is effective for preventing hot air from entering the air-intake-side, thereby avoiding the location of the generator, to be mounted near the engine, from being restricted in design owing to the flow of intake air to provide an improved freedom in location layout of the alternating-current generator. Further, during the halt condition of the generator, it is possible for the wall means to limit hot air, which remains in the belt cover of the generator, from being transferred to the air intake side. Thus, only consideration has to be undertaken for the technologies for discharging heat from the room section defined at the intake air passage side by the wall means and for taking a measure to achieve cooling operation, thereby preventing the temperature of intake air from being adversely affected with hot air produced by the generator after its operation has been terminated to ensure smooth re-startup of the engine.
Preferably, the engine comprises the V-type engine with the cylinder block configured in the V-shape. The aforementioned wall means divides the engine room into at least two room sections, one of which accommodates the engine-room-side communicating portion of the intake air passage and another one of which accommodates the aforementioned alternating-current generator, with the engine cover having intake air introducing ports at respective room sections.
Thus, the presence of the intake air introducing port for the alternating-current generator improves the freedom in layout of the generator and also enables the generator to be effectively cooled. In addition, since the wall means for dividing the engine room into the two room sections is placed along the outer side periphery of the V-type engine, the outer side periphery of the V-shaped configuration which is expanded can be effectively utilized. As a result, the outward extension (that is not the length in the vertical direction but is the amount of inward protrusion) of the partition wall which is constituted with the wall means is selected to have a small value. Since, further, the amount of extension of the partition wall is small, it is possible to fabricate the engine cover which has a deeply indented and downwardly facing bowl configuration.
In a case where the aforementioned wall means is located along the outer side periphery of the aforementioned cylinder head cover of the engine, the flat surface of the cylinder head cover can be utilized, thereby preferably providing an ease of locating the wall means. The cylinder head cover may be made of, for example, plastic material in the illustrated embodiment of the present invention.
Dividing the aforementioned engine room including the exhaust manifold extending from the cylinder head into the two room sections with the wall means enables the surrounding temperature at the air intake side of the engine room to be totally prevented from being adversely affected with exhaust emissions.
The engine room, which is divided into the two room sections with the wall means, is interconnected at the lower half portion with the intake air side, and the sectional area of the opening of the outside air introducing port of the air intake side is designed to be larger than that of the opening formed at the side of the alternating-current generator. That is, as the amount of fresh air to be sucked at the air intake side increases, the temperature of intake air decreases, making it possible to smoothly suck hot air from the side of the generator.
The outboard engine assembly may include the intake silencer which is located in the intake air passage above the cylinder block. By locating the wall means with the use of the relatively flat surface of the intake silencer, the wall means is effective for improving the sealing property at the divided area of the engine room.